Heat exchanger with self-draining tube surface



Sept. 13,1927. R. JONES HEAT EXCHANGER WITH SELF DRAINING TUBE SURFACE Filed April 8,- 1926 2 Sheets-Sheet 1 INVENTOR: 7?:/.s.se// C J0/7e5; 7

BY mkw H15 ATTORNEYS I 1,641,975 p 1927- R. c. JONES HEAT EXCHANGER WITH SELF DRAINING TUBE SURFACE Filed April 8. 1926 2 Sheefos-Sheet 2 INVENTOR Passe/ICJ'ane H15 ATTORNEYS Patented Sept. 13, 1927.

UNITED ST TES RUSSELL 0. Jonas, or imonxv'rnnn, NEW YORK, ASSIGNOR TO THE enrsoom-nussnnn COMPANY, OF NEW YORK, N. Y.,

A CORPORATION OF DELAWARE.

HEAT EXCHA NGER WITH SELF-DRAINING TUBE SURFACE.

Application filed. April 8, 1926. Serial No. 100,520.

The present invention relates to heat exchangers and has to do particularly with the construction of the heating element of the heat exchanger in such fashion as to afford a heat transferring surface of maximum effectiveness, and contemplates particularly a heat exchanger embodying a tubular heat transferring element whereinthe under surface of each tube is'protected from condensate draining from other tubes or from other portions of the tube so that an increased capacity of the heat transferring surface is secured.

The invention pertains chiefly to that class of apparatus,such.. as heaters, condensers, and the like-wherein one of the heat transferring fluids is a condensable vapor such as steam, which is completely condensed on the heat transferring surfaces of the apparatus. In this type of apparatus, the heat transferring element commonly consists of a; plurality of closely rouped tubes which extend longitudinally o the apparatus and serve to convey through it one of the heat transferring mediums. The steam is usually admitted to the space surrounding the tubes and condenses upon the outertube surfaces to thus effect the requisite heat transfer through the tube walls to the fluid within the tubes. Tubes of circular cross-section have-heretofore been used generally for heat exchangers of all kinds but tubes of different cross-section have been proposed in some instances, to securegreater surface'inproportion to the cross-section of the tube and for other purposes.

In my prior Patent, No. 1,549,489, granted August 11, 1925, there is disclosed an oil cooler in which the tubes are formed with a longitudinal depression in at least one side so that the viscous liquid is maintained in the form of a stream, all particles of which are close to the wall of the tube, with the result that an increased velocity of flow is obtained to thereby prevent the formation of a film of the liquid adhering to the wall of the tube, where it would serve to prevent an effective heat transfer. In that aparatus the fluid in the shell is a cooling iquid. having a generally longitudinal flow through the shell so that the. position of the tubes in the shell'is not important. When, however, the structure shown in that patent is'used as a condenser or heater with steam in the space surrounding the tube, the strucprovided Wlth it reentrant groove, the dis- 1 ture is open to the objection that condensate accumulating in the longitudinal depression extending along the tubes blankets a substantial proportion of the heat transferring surface with a relatively poor conducting layer of condensate and thus materially hampers the heat transferring efficiency of the apparatus.

It is a princlpal object of this invention to provide a heater or condenser employing heat transferring tubes in which the heat transferring surface is not impaired by a layer of condensate in the manner described. To this end the tubes are preferably provided with longitudinally extending grooves, and are mounted in the heat exchanger in such fashion that the grooves face downwardly. With this arrangement, the upper surface of thetube is continuously convex and thus serves to effectively shed the'water or condensation accumulating on it. The lower surface of the tube is concave and, being reentrant with respect to the" upper surface, is efiectually protected from the condensate draining ofl the upper surface of the tube or dripping from other tubes. Thus, the lower or reentrant pbrtion of the tube surface, which amounts to approximately fifty per cent of the total heat transferring surface of the tube is effectively protected from condensate and is thus maintained at its best heat transferring efliciency.

By means of this invention, it'is possible to provide a heat exchanger of this typewhich not only incorporates the advantage of maintaining a large proportion of the heat transferring surface free from an obheat exchanger which incorporates the advantages above noted and in addition provides for the inclusion in the heat exchanger of an increased area of heat transferring surface corresponding to a iven available circulating space for the eating steam. Due to'the fact that each of the tubes is placement of each of the tubes is materially reduced, thus affording a correspondingly increased steam space. The tubes may therefore be installed more closely together in order to take advantage of this available increase in steam space and still permit of p a proper balance between the steam space available and the amount of heat transferring surface. This feature is of notable value in heat exchangers employing a bowed tube construction. In apparatus of this type, an increased clearance is necessary to permit fiexure of the bowed tubes under the influence of temperature change. \Vith the structure of the present application, ample clearance is obtainable without necessity of resorting to objectionably wide spacing of the heat exchanging tubes, and there is no tendency to formation of condensate on the tubes.

A preferred embodiment of the invention is illustrated in the accompanying drawings in which:

Fig. 1 is a longitudinal sectional view of a. straight-tube apparatus embodying the present invention;

Fig. 2 is a transverse sectional view taken along line 2-2 of Fig. 1, sighting in the direction of the arrows, and illustrating the construction and arrangement of the heat transferring units;

Fig. 3 is a detail view showing several different forms of the tube of the present invention which may be employed, and

Fig. 4 is a modification of the invention embodied in a bowed-tube apparatus.

Referring to the drawings, 1 indicates the containing shell of the apparatus and 2 indicates the heat transferring tubes. Liquid is admitted to the apparatus through the inlet opening 3 and traverses the heat transferring tubes 2, which as shown in Fig. 1 may be divided to form two successive passes. The liquid then issues from the apparatus through the discharge opening 4. Heating steam is admitted through the inlet opening 5 to the space surrounding the heat transferring tubes 2 and by circulation about within the shell 1 is brought into repeated contact with the tube surfaces and is condensed, the condensate being discharged from the apparatus through the opening 6 rovided at the bottom of the shell 1 for t at purpose. The tubes are supported at their respective ends by means of suitable tube sheets 7 and 7 into which the ends of the respective tubes are expanded or otherwise secured. As shown, the tube sheet 7 forms part of a floating head connecting the two passes of the heater as is common in apparatus of this class.

The construction of the heat transferring tubes 2 and the positioning of these tubes in the shell is shown in detail in Fi ure 2. The intermediate portion of eac tee ers of the tubes is provided with a longitudinal depression 8 which extends throughout substantially the entire portion of the tubes lying intermediate the tube sheets 7 and 7. The upper portion of the tube surface indicated at 9 is substantially semi-circular in section and thus presents a sloping surface from which accumulated condensate readily drains. The longitudinal depression 8 occurs at the under side of the tube and, as is evident from the drawings, is protected from condensate draining off the upper surface portion 9 of the tube or dripping from other tubes. This lower groove or reentrant portion of the surface constitutes substantially fifty per cent of the total heat transferring surface of the tube and is at all times protected from an objectionable film of condensate with the result that a material increase in the heat transferring efficiency of the apparatus is effected. It is evident that certain variations in the shape of the tube section may be made and some such variations are shown in detail in Figure 3.

The cross sectional area of the tubes is substantially reduced by reason of the provision of the groove 8. The result is that the liquid traversing the tubes is filmed out in a fiat stream, all points of which are closely adjacent the tube walls. This affords a particularly effective heat transfer in the case of oils and similar liquids wherein there is a tendency toward the formation of a congealed layer of liquid immediately adjacent the cooling surfaces.

Due to the reduced cross sectional area of the present tubes, an increased amount of steam space is made available. This increased space is proportional to the diiference betweenthe area of the original circular cross section of the tube and the cross sectional area of that portion of the tube having the longitudinal depression 8 formed in it. This feature may most effectively be taken advantage of by spacing the tubes in more closely adjacent relation.

In the bowed tube construction shown in Fig. l of the drawings it will be noted that the provision of the groove on the under side of each tube allows the next lower tube a greater relative freedom of movement without danger of interference between tubes. Also, this reduction in the interior volume of the shell of the exchanger of the present invention which is occupied by the tubes of the present invention constitutes a great improvement over the ordinary exchanger with plain eircular tubes. For, in this latter type of exchangers, it is usually necessary to provide a large number of passes for the fluid,--sometimes as high as six-, in order to accomplish results at all approaching those effectuated by the present invention. This necessitates numerous partitions in the fluid-headersthat is, the oil or water headersand naturally opposite these header-partitions, whole rows of tubes must be omitted, which radically reduces the amount of surface which can be installed in the heat-exchanger. With the present design, on the other hand, it is never necessary to provide more than two passes, and frequently it is sufficient to have one pass with an outside-packed, floating head.

I claim:

1. In a heat exchanger ofthe class described, a shell, heat transferring tubes within said shell and presenting a convex upper surface and a concave lower surface throughout their entire length within the heat-transferring space of the exchanger.

2. In a heat exchanger of the class described, a shell, heat transferring tubes within said shell and presenting an upper surface having a downward slope at every point throughout their entire lengthwithin theheat-transferring space of the exchanger and a lower surface reentrant with respect to said upper surface to a suflicient degree to yrender said lower surface protected from condensate flowing over said upper surface. 3. A heat exchanger of the class described,

comprising a shell for receiving heating vapors and tubes for conducting another fluid into heat exchanging relation with said vapors, each of said tubes being longitudinally-bowed from end to end and provided I with a longitudinally extending depression faced downwardly away from the precipitation of said condensing heating vapors.

4. A heat exchanger comprising a shell, tubes having a convex peripheral portion and a concave peripheral portion, said concave portion being faced downwardly away from the precipitation of the condensing heating vapors, and supports for the ends of said respective tubes,-said tube ends being of continuously convexperiphery.

5. A heat exchanger of the class described comprising a shell for containing the heating steam and tubes having end portions of circular section and intermediate portions distorted from a circular section a sufficient amount to effect a reduction in cross sectional area and having a downwardly faceddepression, the transverse dimension of the intermediate portions of the tubes being less than the diameter of the circular portions of said tube's.

6. A heat exchanger of the class described, comprising a shell providing a space for the heating steam and having a plurality of heat transferring tubes therein, each of said tubes having a convex upper surface and a broad, concave lower surface, hearing such a relation to the total tube surface, that substantially one-half of the total tube surface faces away from the deposit of condensate.

whereof I aflix my signature. I

In testimony RUSSELL C. JONES. 

